One of the most critical components of any project management process is to fulfill the endeavor of keeping everyone who needs to be in the loop on all of the big and small ticket items that may arise over the course of the project, actually in that loop, and as such developing and maintaining a thorough and convenient means of communication which accomplishes this. And one of the most important groups of individuals to keep in the loop is those who have a financial stake in the project in question. This involves the complete act of managing the stakeholders. The act of managing the stakeholders invokes the complete and thorough process of managing all of those communications that are meant to provide information to all of the relevant stakeholders. The act of managing the stakeholders also involves resolving any issues that may have arisen as a result of the act of communication with the stakeholders, as well as the act of addressing any concerns that the stakeholder may have voiced.
This term is defined in the 3rd edition of the PMBOK but not in the 4th.